1. Field of the Invention
The present invention relates to an oxide semiconductor film, a transistor, a semiconductor device, and manufacturing methods thereof.
In this specification, a semiconductor device refers to all types of devices which can function by utilizing semiconductor characteristics; an electro-optical device, a semiconductor circuit, and an electronic appliance are all semiconductor devices.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor using a semiconductor thin film formed over a substrate having an insulating surface (also referred to as thin film transistor (TFT)). The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (display device). A silicon-based semiconductor material is widely known as a material for a thin semiconductor film applicable to a transistor.
Further, recently, an oxide semiconductor has been attracting attention as a material of a thin semiconductor film. For example, a transistor whose semiconductor layer including an amorphous oxide containing indium (In), gallium (Ga), and zinc (Zn) (an In—Ga—Zn—O-based amorphous oxide) is formed over a substrate is disclosed (see Patent Document 1).